JP2000034553A - Continuous plating method for steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a cold rolled plated steel sheet by only one line by providing the stream upper than a plating means with a pickling means and one stand of cold rolling mill and forming a hot rolled steel sheet into a cold rolled plated steel sheet under specified conditions. SOLUTION: A hot rolled steel sheet of 1.0 to 1.2 mm thickness unwound from a reel 1 is fed to a pickling tank 4 via a welder 2 and an inlet side looper 3, scale is removed from the surface of the steel sheet, and washing by water and drying are executed. This steel sheet is fed to a cold rolling mill having a pair of work rolls 5a and 5b with backup rolls and bridle rolls 5c and 5d before and behind and is rolled to a thickness of 0.6 to 1.0 mm. Next, it is heated and annealed by an annealing furnace 6 having a heating zone 6a, a reducing zone 6b and a cooling zone 6c, is fed to a zinc bath pot 7, is hot dip galvanized and, via a galvannealing zone, is cooled at an air cooling part 10 and a water cooling part 11. This cold rolled plated steel sheet is coiled by a coiling reel 17 via a skin pass mill 12, a tension labeler 13, a chemical conversion treating zone 14 or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The claimed invention relates to the claimed invention.
The present invention relates to a continuous plating line for continuously producing a plated steel sheet having a thickness of about 1.0 mm, and a method for continuously plating a steel sheet using the same.

[0002]

2. Description of the Related Art Galvanized steel sheets having a thickness of 1 mm or less are
Conventionally, it is manufactured as follows. That is, first, a steel sheet (hot-rolled steel sheet) having a thickness of 2.0 to 4.0 mm is obtained by hot rolling, passed through a pickling line, sent to a cold rolling line, and then passed through a galvanizing line. The galvanizing line is generally configured as shown in FIG. 2, and is disposed between the upstream reel 1 and the downstream reel 17.
Along with the welder 2, the loopers 3 and 15, the annealing furnace 6, and the like, a galvanizing pot 7 as plating means and the like are arranged. On the downstream side of the pot 7, a galvanizing zone 9, a skin pass mill 12, a tension leveler (not shown), a chemical conversion treatment facility (the same), and the like may be provided as necessary. In addition, the cold rolling line used prior to plating is conventionally provided as one independent line as described above separately from the pickling line and the plating line.
In other words, in a cold rolling line, a reverse rolling mill or a tandem rolling mill generally performs a plurality of passes on a hot-rolled steel sheet having a thickness of 2.0 to 4.0 mm to a thickness of 0.2 to 1.2 mm. Rolled up.

[0003] The thickness of the material used in the above is 2.0 to 4.
To obtain a hot-rolled steel sheet of 0 mm, the thickness is 200-250 m
Generally, a continuous cast piece (slab) having a length of about m is hot-rolled. However, in recent years, the technological development of so-called continuous thin slab casting has been advanced, so that a thin continuous cast piece (thin cast piece) having a thickness of about 50 mm is manufactured and the cast piece is directly hot-rolled on the same line. Then, it can be wound into a coil to form a hot-rolled steel sheet. Even in the case of thin slab continuous casting, when producing a plated steel sheet, a hot-rolled steel sheet having a thickness of 2.0 to 4.0 mm is formed, and then is applied to each line of pickling, cold rolling, and plating. It is done by passing through.

[0004] The steps required to obtain a galvanized steel sheet from the continuous cast piece described above are described in, for example, "Revised Thin Sheet Manual" (edited by the Iron and Steel Institute of Japan, Steel Sheet Subcommittee).
This is described in FIG. 2.1 on page 5. For details on the galvanizing line, see, for example, “(Nishiyama Memorial Technical Lecture, 106th / 107th) Advances in Manufacturing Technology of Hot Dip Galvanized Steel Sheet” (Japan Iron and Steel Association), page 4, FIG.
It is described in. For thin slab continuous casting, see “Pr
oduction of 1 mm thick hot rolled steel strip ''
(MPT International 1/1998), pages 50-51.

[0005]

In order to produce a galvanized steel sheet as described above, the steel sheet obtained by hot rolling must be passed through three more lines. That is, they are pickling, cold rolling, and plating lines.

When the number of lines is large as described above, there are the following disadvantages. First, the number of independent equipment required is the same as the number of lines, which requires considerable equipment costs, and requires considerable space in the steelworks for equipment arrangement. The leading and trailing ends of the steel plate are easily damaged or defective in each line, and the costs associated with moving between the lines are also generated, so the larger the number of lines, the higher the running cost . In addition, because of the convenience of setup for each line, it is rare that a steel sheet that has been processed in one line can be immediately sent to the next line, and therefore it will take a long time for the product to be completed through all lines. There is also a disadvantage that it takes time.

An object of the present invention is to provide a continuous plating line for a steel sheet which can be used as a hot-rolled steel sheet by using only one line, and a continuous plating method using the same.

[0008]

A continuous plating line for a steel sheet according to claim 1 is a line (equipment) for continuously plating a steel sheet, wherein the pickling means and the cold rolling are provided upstream of the plating means. Machine is arranged. In addition, since it is a continuous plating line for steel sheets, in this line, there are appropriate plating means such as a pot filled with molten zinc, etc., as well as reels, loopers, annealing furnaces, and, if necessary, A skin pass mill, a tension leveler and the like are provided.

In the continuous plating line according to the first aspect, when a steel sheet obtained by hot rolling is passed through the line, the following processing is sequentially performed on the steel sheet. That is, the steel sheet is unwound from the reel on the upstream side and the steel sheet is fed, pickled (and washed / dried) by pickling means to remove the scale on the surface, rolled by a cold rolling mill, and then subjected to ordinary continuous plating. As in the case of the line, annealing and plating, galvanizing treatment, skin pass rolling, and the like are performed as necessary, and then the film is wound on a downstream reel.

In other words, according to this plating line, the hot-rolled steel sheet can be pickled, cold-rolled and plated by merely passing it through the line as described above. Because hot-rolled steel sheets can be made into plated steel sheets with only one line, unlike conventional cases where many lines are required, equipment costs, installation space, running costs, and even the production period of plated steel sheets Is advantageous. Such advantages are provided because the plating line incorporates the pickling means and the cold rolling mill in the same line. The reason that such embedding became possible is that
This is because a hot-rolled steel sheet having a thickness of about 1.0 to 1.2 mm can be commercially produced, so that cold rolling can be performed in one to two passes. Since only one or two passes are sufficient, the cold rolling mill can be incorporated in this plating line, and it is not difficult to arrange the pickling means immediately upstream of the same line in the same line. .

In a cold rolling mill having a small number of passes, it is usually not easy to realize a high rolling reduction. If a general cold rolling mill is provided with only one stand, the rolling reduction is at most about 40%, which is lower than the rolling reduction (70-80%) in a conventional ordinary cold rolling line. However, such a cold-rolled steel sheet having a low draft ratio is not optimal in r value showing the drawing characteristics, but has a sufficient use as a light-working steel sheet or the like in which deep drawing is not scheduled.

[0012] Recent advances in continuous casting technology called thin slab casting have made it possible to obtain slabs having a thickness of about 50 mm (described above). It is no longer impossible to commercially produce a hot-rolled steel sheet having a thickness of about 1.0 to 1.2 mm by cold rolling. For example, if such a hot-rolled steel sheet is passed through the continuous plating line of claim 1, the hot-rolled steel sheet can be made into a plated steel sheet having a thickness of about 0.6 to 1.0 mm by only one line.

A continuous plating line according to a second aspect of the present invention is characterized in that the cold rolling mill comprises one stand.

Such a plating line has an advantage that it can be incorporated at low cost because the cold rolling mill has only one stand. Further, if a hot-rolled steel sheet having a thickness of about 1.0 to 1.6 mm is used as a raw material, it can be rolled to a thickness of 0.6 to 1.0 mm even if the cold rolling mill is only one stand, Therefore, the production of the cold-rolled steel sheet can be efficiently performed.

According to a third aspect of the present invention, the continuous plating method has a thickness of 1.2 mm.
The pickling, the cold rolling, and the plating are continuously performed by passing a hot-rolled steel sheet having a thickness of not more than 1 mm through a continuous plating line according to claim 1 or 2.

Since the above-mentioned continuous plating line is used, this plating method uses a hot-rolled steel sheet having the above-mentioned thickness as a material, and has a thickness of 0.6 to 0.6 mm only by the plating line.
A cold-rolled steel sheet (eg, zinc-plated or aluminum-plated) of about 1.0 mm can be manufactured at low cost.

A continuous plating method according to a fourth aspect is characterized in that the hot-rolled steel sheet according to the third aspect is obtained by hot rolling a thin slab obtained by continuous casting (so-called thin slab continuous casting). And The term “thin cast slab” refers to a cast slab whose thickness can be easily reduced to 1.2 mm or less by hot rolling, and generally about 50 mm.

In particular, this continuous plating method is to produce a steel sheet having a thickness of 1.2 mm or less by hot rolling a thin slab obtained by continuous thin slab casting as described above, and using it as a material. Therefore, the production cost of the hot-rolled steel sheet is extremely advantageous. In other words, 20
If a normal continuous cast piece (slab) having a thickness of 0 mm or more is hot-rolled, the thickness of the steel sheet (hot-rolled steel sheet) is reduced to 1.2 mm.
mm or less is commercially difficult. Hot rolling of slabs of normal thickness to such a small thickness requires the use of extremely specialized rolling equipment, etc., and is not commercially viable (that is, considering cost). It is. In this regard, this plating method described in claim 4 is to produce a steel sheet having a thickness of 1.2 mm or less by hot rolling a thin-walled slab as described above, and can be implemented commercially. Have been. As described above, commercial production of thin slab casting has been started in recent years (the cost of the casting equipment is lower than that of ordinary continuous casting), and a tunnel furnace etc. is placed in front of the finishing mill. This is because the rolling temperature can be maintained high, and commercial production up to a thin sheet of 1.0 mm is possible.

[0019]

FIG. 1 shows an embodiment of the present invention. FIG. 1 is a schematic diagram of a continuous hot-dip galvanizing line, in which the flow of a series of steel sheets is divided into figures (a), (b), and (c) in order from the upstream side.

The following equipment is arranged in the hot-dip galvanizing line. First, at the most upstream portion shown in FIG. 1A, an unwinding reel 1, a welder 2, an entry-side looper 3, a pickling tank 4, and a cold rolling mill 5 are arranged in this order. The reel 1 is configured so that two coils of a steel plate can be set at the same time, so that when the unwinding of the steel plate from one coil is completed, the unwinding can be continuously performed from the other coil. The welder 2 is used to connect the ends of the steel plates when switching coils, for example. The looper 3 is made up of a plurality of rolls whose positions are variable, and a steel plate is hung thereon. By changing the position of the rolls, it is possible to absorb a speed difference between the upstream and downstream steel plates. This makes it possible to feed the steel sheet at a constant speed to the downstream side even when it is running. The pickling tank 4 is a means for removing scale (iron oxide film) from the surface of the steel sheet before rolling, and includes a pickling portion, a water washing portion, and a drying portion (each portion is not shown). As the cold rolling mill 5, a non-reversing six-layer rolling mill having a backup roll on the outside (up and down) together with a pair of work rolls 5a and 5b is provided only in one stand, and before and after that, a constant tension is applied to the steel sheet. Are arranged.

In the middle part shown in FIG. 1B, an annealing furnace 6, a zinc bath pot 7, a galvaneal zone 9, and the like are arranged. As the annealing furnace 6, heating zones 6a are sequentially arranged from the upstream side.
And a zone having a reduction zone 6b and a cooling zone 6c, so that the steel sheet immediately before plating can be heated and annealed without being oxidized. The pot 7, which is a plating means, is a container in which molten zinc is stored so as to immerse a steel plate, and is provided with an air knife 8 at an upper portion for adjusting a plating thickness. Further, the galvaneal zone 9 is a heat treatment apparatus for reducing the porosity of the plating layer. The steel sheet heated in these portions is cooled in the subsequent air cooling unit 10 and water cooling unit 11.

In the most downstream portion shown in FIG. 1C, a skin path mill 12, a tension leveler 13,
Chemical treatment zone 14, outlet looper 15, oiling device 1
6 and the take-up reel 17 are arranged in this order. A shear (cutting machine) may be provided in front of the reel 17. The skin pass mill 12 is used to reduce the rolling reduction of 1 to 3 to a plated steel sheet.
% To reduce the yield elongation and smooth the surface by applying light pressure of about%. The tension leveler 13 enhances flatness by applying tension to the steel sheet to correct the wave of the steel sheet due to edge elongation or medium elongation. The chemical conversion treatment zone 14 is a means for performing a chromate treatment or the like on the steel sheet.

In this example, a hot-rolled steel sheet (hot coil) having a thickness of 1.2 mm or 1.0 mm is passed through the zinc plating line configured as described above. However, as the hot rolled steel sheet, a thin slab having a thickness of 50 mm manufactured by so-called continuous thin slab casting and rolled to the thickness is used. This is because if a normal continuous cast slab having a thickness exceeding 200 mm is to be hot-rolled to such a thickness, a huge cost is required due to the necessity of a special hot-rolling mill.

When the above hot-rolled steel sheet is passed through the continuous plating line of FIG. 1, the steel sheet is removed from the scale in the pickling tank 4 while passing through the line, and the cold-rolled mill 5 And then annealed in an annealing furnace 6 and then galvanized in a zinc bath pot 7. Thereafter, the steel sheet is subjected to a galvanizing treatment in a galvanizing zone 9, and the smoothness and flatness of the surface are increased by a skin pass mill 12 and a tension leveler 13. It is wound up.

Since the cold rolling mill 5 has only one stand and is not of the reversing type and does not pass the steel sheet a plurality of times, this line is simple in terms of equipment, but the reduction rate of the steel sheet is low. Is as low as about 40% or less. However, since the material is a hot-rolled steel sheet having a thickness of 1.2 mm or 1.0 mm as described above, this line requires 0.6 to 0.8 mm.
It is possible to obtain a cold-rolled plated steel sheet having a thickness of about mm or about the same. Since the reduction ratio is not high, the drawing characteristics of the product are slightly inferior to the conventional products with 70-80% reduction. is there.

It should be noted that the continuous plating line shown in FIG. 1 is not limited to a hot-dip galvanized product of a cold-rolled steel sheet. This is because other products can be manufactured by this line in the following manner. That is, a) If a steel sheet is passed while the work rolls 5a and 5b of the cold rolling mill 5 are open, a galvanized product of a hot-rolled steel sheet that is not subjected to cold rolling can be manufactured.

B) By putting molten aluminum or the like in place of the molten zinc in the pot 7, which is a plating means, it is possible to manufacture a steel plate which is not galvanized but aluminum plated.

C) If no molten metal is put in the pot 7, an annealed cold-rolled steel sheet which has been cold-rolled and not plated can be obtained. At that time, if
If cold rolling is not performed in the same manner as in a), a hot-rolled steel sheet subjected to only pickling can be obtained.

D) The required steel sheet can be produced at a desired cost by appropriately selecting the use or non-use of the galvanizing zone 8, the skin pass mill 12, the tension leveler 13, and the chemical conversion zone 14 downstream of the pot 7. can do.

Although FIG. 1 and the above show a case where the cold rolling mill 5 has one stand, it is of course possible to use two cold rolling mills 5. In that case, the rolling reduction of the steel sheet can be made higher than in the above-described case, and a thinner steel sheet can be manufactured.

[0031]

According to the continuous plating line for a steel sheet according to the first aspect, each of the pickling, cold rolling, and plating processes is performed on the steel sheet by passing the hot-rolled steel sheet only through the plating line. Can be. By installing this plating line, it can be said that the pickling line and the cold rolling line, which were conventionally required, become unnecessary. Since hot-rolled steel sheets can be converted into plated steel sheets with only one line, there are significant advantages in terms of equipment costs, installation space, running costs, and the production period of plated steel sheets.

The continuous plating line according to the second aspect of the present invention suffices to install one very common cold rolling mill, so that it is configured as a compact one having a simple facility arrangement.

According to the method for continuously plating steel sheets according to the third aspect, a cold-rolled plated steel sheet having a thickness of about 0.6 to 1.0 mm can be manufactured at low cost by using only one line.

In the continuous plating method for a steel sheet according to the fourth aspect, a thin steel sheet obtained by hot rolling a thin cast slab by continuous thin slab casting or the like is used as a material.
m can be manufactured inexpensively and in a short time. The reason for being inexpensive is that the cost for obtaining a hot-rolled steel sheet from a thin cast slab is not high, and that the hot-rolled steel sheet can be easily processed in the plating line.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of the present invention,
It is a schematic diagram of a hot-dip galvanizing line. Fig. 1 (a)
(B) and (c) show the flow of a series of steel sheets in the line in order from the upstream side.

FIG. 2 is a schematic view showing a conventional general continuous galvanizing line.

[Explanation of symbols]

 4 Pickling tank (pickling means) 5 Cold rolling mill 6 Annealing furnace 7 Zinc bath pot (plating means)

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[Procedure amendment]

[Submission date] June 21, 1999 (1999.6.2
1)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction contents]

[Document Name] Statement

[Title of the Invention] Continuous plating method for steel sheet

[Claims]

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The claimed invention is characterized by 0.6
Continuous production of plated steel sheet with thickness of ~ 1.0mm
The present invention relates to a method for continuously plating steel sheets.

[0002]

2. Description of the Related Art Galvanized steel sheets having a thickness of 1 mm or less are
Conventionally, it is manufactured as follows. That is, first, a steel sheet (hot-rolled steel sheet) having a thickness of 2.0 to 4.0 mm is obtained by hot rolling, passed through a pickling line, sent to a cold rolling line, and then passed through a galvanizing line. The galvanizing line is generally configured as shown in FIG. 2, and is disposed between the upstream reel 1 and the downstream reel 17.
Along with the welder 2, the loopers 3 and 15, the annealing furnace 6, and the like, a galvanizing pot 7 as plating means and the like are arranged. On the downstream side of the pot 7, a galvanizing zone 9, a skin pass mill 12, a tension leveler (not shown), a chemical conversion treatment facility (the same), and the like may be provided as necessary. In addition, the cold rolling line used prior to plating is conventionally provided as one independent line as described above separately from the pickling line and the plating line.
In other words, in a cold rolling line, a reverse rolling mill or a tandem rolling mill generally performs a plurality of passes on a hot-rolled steel sheet having a thickness of 2.0 to 4.0 mm to a thickness of 0.2 to 1.2 mm. Rolled up.

[0003] The thickness of the material used in the above is 2.0 to 4.
To obtain a hot-rolled steel sheet of 0 mm, the thickness is 200-250 m
Generally, a continuous cast piece (slab) having a length of about m is hot-rolled. However, in recent years, the technological development of so-called continuous thin slab casting has been advanced, so that a thin continuous cast piece (thin cast piece) having a thickness of about 50 mm is manufactured and the cast piece is directly hot-rolled on the same line. Then, it can be wound into a coil to form a hot-rolled steel sheet. Even in the case of thin slab continuous casting, when producing a plated steel sheet, a hot-rolled steel sheet having a thickness of 2.0 to 4.0 mm is formed, and then is applied to each line of pickling, cold rolling, and plating. It is done by passing through.

[0004] The steps required to obtain a galvanized steel sheet from the continuous cast piece described above are described in, for example, "Revised Thin Sheet Manual" (edited by the Iron and Steel Institute of Japan, Steel Sheet Subcommittee).
This is described in FIG. 2.1 on page 5. For details on the galvanizing line, see, for example, “(Nishiyama Memorial Technical Lecture, 106th / 107th) Advances in Manufacturing Technology of Hot Dip Galvanized Steel Sheet” (Japan Iron and Steel Association), page 4, FIG.
It is described in. For thin slab continuous casting, see “Pr
oduction of 1 mm thick hot rolled steel strip ''
(MPT International 1/1998), pages 50-51.

[0005]

In order to produce a galvanized steel sheet as described above, the steel sheet obtained by hot rolling must be passed through three more lines. That is, they are pickling, cold rolling, and plating lines.

When the number of lines is large as described above, there are the following disadvantages. First, the number of independent equipment required is the same as the number of lines, which requires considerable equipment costs, and requires considerable space in the steelworks for equipment arrangement. The leading and trailing ends of the steel plate are easily damaged or defective in each line, and the costs associated with moving between the lines are also generated, so the larger the number of lines, the higher the running cost . In addition, because of the convenience of setup for each line, it is rare that a steel sheet that has been processed in one line can be immediately sent to the next line, and therefore it will take a long time for the product to be completed through all lines. There is also a disadvantage that it takes time.

[0007] The claimed invention has an advantage that a hot-rolled steel sheet can be made into a plated steel sheet by only one line.
It is an object of the present invention to provide a continuous plating method for a steel sheet having the same.

[0008]

Means for Solving the Problems] continuous plating process of steel sheet according to claim 1 is a method for continuously plating a steel sheet, pickling means and a stun upstream of the plating unit
Using a continuous plating line with a cold rolling mill
A hot-rolled steel sheet having a thickness of 1.0 to 1.2 mm is
Pickling and cold rolling by passing through
Rolling continuously, cold rolling 0.6-1.0mm thick
It is characterized by obtaining a steel plate. Since the above line is a continuous plating line for steel sheets, in this line, there are appropriate plating means such as pots containing molten zinc, etc., as well as reels and loopers, annealing furnaces, and if necessary It shall be provided with a galvanile belt, skin pass mill, tension leveler and the like.

For use in the plating method of claim 1,
When the steel sheet obtained by hot rolling is passed through the continuous plating line, the following processing is sequentially performed on the steel sheet. That is, the steel sheet is unwound from the reel on the upstream side and the steel sheet is fed, pickled (and washed / dried) by pickling means to remove the scale on the surface, rolled by a cold rolling mill, and then subjected to ordinary continuous plating. As in the case of the line, annealing and plating, galvanizing treatment, skin pass rolling, and the like are performed as necessary, and then the film is wound on a downstream reel.

[0010] That is, the claim using this plating line
According to the method 1 , the hot-rolled steel sheet can be pickled, cold-rolled, and plated by merely passing it through the line as described above. Because hot-rolled steel sheets can be made into plated steel sheets with only one line, unlike conventional cases where many lines are required, equipment costs, installation space, running costs, and even the production period of plated steel sheets Is advantageous. Such advantages are provided because the plating line incorporates the pickling means and the cold rolling mill in the same line. Such incorporation of becomes available, as cold rolling by hot rolling steel plate having a thickness of about 1.0~1.2mm became commercially viable production suffice 1-2 pass Because it has become.
Since only one or two passes are sufficient, the cold rolling mill can be incorporated in this plating line, and it is not difficult to arrange the pickling means immediately upstream of the same line in the same line. .

In a cold rolling mill having a small number of passes, it is usually not easy to realize a high rolling reduction. Since only one stand is provided for a general cold rolling mill, the rolling reduction is at most about 40%, which is lower than the rolling reduction (70-80%) in a conventional ordinary cold rolling line. However, such a cold-rolled steel sheet having a low draft ratio is not optimal in r value showing the drawing characteristics, but has a sufficient use as a light-working steel sheet or the like in which deep drawing is not scheduled.

[0012] Recent advances in continuous casting technology called thin slab casting have made it possible to obtain slabs having a thickness of about 50 mm (described above). It is no longer impossible to commercially produce a hot-rolled steel sheet having a thickness of about 1.0 to 1.2 mm by cold rolling. For example, if such a hot-rolled steel sheet is passed through the continuous plating line of claim 1, the hot-rolled steel sheet can be made into a plated steel sheet having a thickness of about 0.6 to 1.0 mm by only one line.

[0013] The series used in the method of claim 1.
The continuous plating line has an advantage that it can be incorporated at low cost because the cold rolling mill has only one stand. Further, if a hot-rolled steel sheet having a thickness of about 1.0 to 1.6 mm is used as a material, a thickness of 0.6 to 1.
Rolling to 0 mm is possible, and therefore, cold-rolled plated steel sheets can be manufactured efficiently.

[0014] The plating method of claim 1 has a thickness of 1.0 to 1.0.
Continuous plating line for 1.2mm hot rolled steel sheet as described above
Since the hot-rolled steel sheet having the above thickness is used as the material, the thickness is 0.6 to 1.0 m only by the plating line.
m can be manufactured at a low cost.

The continuous plating process according to claim 2, wherein
The hot rolled steel sheet according to item 1 is characterized in that a thin cast slab obtained by continuous casting (so-called thin slab continuous casting) is hot rolled. "Thin cast slab" refers to a cast slab whose thickness can be easily reduced to 1.0 to 1.2 mm by hot rolling, and is generally 50 mm.
It means something.

In this continuous plating method, a steel sheet having a thickness of 1.0 to 1.2 mm is manufactured by hot-rolling a thin slab by continuous thin slab casting as described above, and this is used as a material. Therefore, the production cost of the hot-rolled steel sheet is extremely advantageous. In other words, ordinary continuous cast slabs (slabs) having a thickness of 200 mm or more as in the past
Is hot rolled, it is commercially difficult to reduce the thickness of the steel sheet (hot rolled steel sheet) to 1.2 mm or less. Hot rolling of slabs of normal thickness to such a small thickness requires the use of extremely specialized rolling equipment, etc., and is not commercially viable (that is, considering cost). It is. In this regard, the plating method described in claim 2 is to produce a steel sheet having a thickness of 1.0 to 1.2 mm in advance by hot rolling a thin cast slab as described above. Has also become feasible. As described above, commercial production of thin slab casting has been started in recent years (the cost of the casting equipment is lower than that of ordinary continuous casting), and a tunnel furnace etc. is placed in front of the finishing mill. So that the rolling temperature can be kept high and 1.0 mm
This is because commercial production is possible up to thin sheets.

[0017] The continuous plating method according to claim 3 is characterized in that
In addition to the galvaneal zone downstream of the plating means,
Skin pass mill, tension leveler and chemical treatment zone
Is used while appropriately selecting non-use.
I do. With this method, the required steel sheet can be obtained.
It can be manufactured at a low cost.

[0018]

FIG. 1 shows an embodiment of the present invention. FIG. 1 is a schematic diagram of a continuous hot-dip galvanizing line, in which the flow of a series of steel sheets is divided into figures (a), (b), and (c) in order from the upstream side.

The following equipment is arranged in the hot-dip galvanizing line. First, at the most upstream portion shown in FIG. 1A, an unwinding reel 1, a welder 2, an entry-side looper 3, a pickling tank 4, and a cold rolling mill 5 are arranged in this order. The reel 1 is configured so that two coils of a steel plate can be set at the same time, so that when the unwinding of the steel plate from one coil is completed, the unwinding can be continuously performed from the other coil. The welder 2 is used to connect the ends of the steel plates when switching coils, for example. The looper 3 is made up of a plurality of rolls whose positions are variable, and a steel plate is hung thereon. By changing the position of the rolls, it is possible to absorb a speed difference between the upstream and downstream steel plates. This makes it possible to feed the steel sheet at a constant speed to the downstream side even when it is running. The pickling tank 4 is a means for removing scale (iron oxide film) from the surface of the steel sheet before rolling, and includes a pickling portion, a water washing portion, and a drying portion (each portion is not shown). As the cold rolling mill 5, a non-reversing six-layer rolling mill having a backup roll on the outside (up and down) together with a pair of work rolls 5a and 5b is provided only in one stand, and before and after that, a constant tension is applied to the steel sheet. Are arranged.

In the middle part shown in FIG. 1B, an annealing furnace 6, a zinc bath pot 7, a galvaneal zone 9, and the like are arranged. As the annealing furnace 6, heating zones 6a are sequentially arranged from the upstream side.
And a zone having a reduction zone 6b and a cooling zone 6c, so that the steel sheet immediately before plating can be heated and annealed without being oxidized. The pot 7, which is a plating means, is a container in which molten zinc is stored so as to immerse a steel plate, and is provided with an air knife 8 at an upper portion for adjusting a plating thickness. Further, the galvaneal zone 9 is a heat treatment apparatus for reducing the porosity of the plating layer. The steel sheet heated in these portions is cooled in the subsequent air cooling unit 10 and water cooling unit 11.

In the most downstream portion shown in FIG. 1C, a skin path mill 12, a tension leveler 13,
Chemical treatment zone 14, outlet looper 15, oiling device 1
6 and the take-up reel 17 are arranged in this order. A shear (cutting machine) may be provided in front of the reel 17. The skin pass mill 12 is used to reduce the rolling reduction of 1 to 3 to a plated steel sheet.
% To reduce the yield elongation and smooth the surface by applying light pressure of about%. The tension leveler 13 enhances flatness by applying tension to the steel sheet to correct the wave of the steel sheet due to edge elongation or medium elongation. The chemical conversion treatment zone 14 is a means for performing a chromate treatment or the like on the steel sheet.

In this example, a hot-rolled steel sheet (hot coil) having a thickness of 1.2 mm or 1.0 mm is passed through the zinc plating line configured as described above. However, as the hot rolled steel sheet, a thin slab having a thickness of 50 mm manufactured by so-called continuous thin slab casting and rolled to the thickness is used. This is because if a normal continuous cast slab having a thickness exceeding 200 mm is to be hot-rolled to such a thickness, a huge cost is required due to the necessity of a special hot-rolling mill.

When the hot-rolled steel sheet is passed through the continuous plating line shown in FIG. 1, the steel sheet is desalted in a pickling tank 4 while passing through the line, and is subjected to a cold rolling mill 5. And then annealed in an annealing furnace 6 and then galvanized in a zinc bath pot 7. Thereafter, the steel sheet is subjected to a galvanizing treatment in a galvanizing zone 9, and the smoothness and flatness of the surface are increased by a skin pass mill 12 and a tension leveler 13. It is wound up.

Since the cold rolling mill 5 has only one stand and is not of the reversing type and does not pass the steel sheet a plurality of times, this line is simple in terms of equipment, but the reduction rate of the steel sheet is low. Is as low as about 40% or less. However, since the material is a hot-rolled steel sheet having a thickness of 1.2 mm or 1.0 mm as described above, this line requires 0.6 to 0.8 mm.
It is possible to obtain a cold-rolled plated steel sheet having a thickness of about mm or about the same. Since the reduction ratio is not high, the drawing characteristics of the product are slightly inferior to the conventional products with 70-80% reduction. is there.

It should be noted that what can be produced by the continuous plating line shown in FIG. 1 is not limited to a hot-dip galvanized product of a cold-rolled steel sheet. This is because other products can be manufactured by this line in the following manner. That is, a) If a steel sheet is passed while the work rolls 5a and 5b of the cold rolling mill 5 are open, a galvanized product of a hot-rolled steel sheet that is not subjected to cold rolling can be manufactured.

B) By putting molten aluminum or the like in place of the molten zinc in the pot 7 which is a plating means, it is possible to manufacture a steel plate which is not galvanized but aluminum plated.

C) If no molten metal is put in the pot 7, an annealed cold-rolled steel sheet which has been cold-rolled and not plated can be obtained. At that time, if
If cold rolling is not performed in the same manner as in a), a hot-rolled steel sheet subjected to only pickling can be obtained.

D) Galvanile zone downstream of pot 7
9 and the skin pass mill 12, the tension leveler 13, and the chemical conversion treatment zone 14, the required steel sheet can be manufactured at a desired cost by appropriately selecting use or non-use.

Although FIG. 1 and the above show a case where the cold rolling mill 5 has one stand, it is of course possible to use two cold rolling mills 5 separately from the claimed invention . In that case, the rolling reduction of the steel sheet can be made higher than in the above-described case, and a thinner steel sheet can be manufactured.

[0030]

The method for continuous plating of a steel sheet according to claim 1
According to the method , by passing a hot-rolled steel sheet through one continuous plating line , each processing of pickling, cold rolling, and plating can be performed on the steel sheet. By installing this plating line, it can be said that the pickling line and the cold rolling line, which were conventionally required, become unnecessary. Since hot-rolled steel sheets can be converted into plated steel sheets with only one line, there are significant advantages in terms of equipment costs, installation space, running costs, and the production period of plated steel sheets.

[0031] The continuous plating line, because those suffices very common cold rolling mill installation one configured as a compact with simple equipment configuration.

According to this continuous plating method, a cold rolled plated steel sheet having a thickness of about 0.6 to 1.0 mm can be manufactured at low cost by only one line.

In the continuous plating method for a steel sheet according to the second aspect , a thin steel sheet obtained by hot rolling a thin cast slab by continuous thin slab casting or the like is used as a material.
m can be manufactured inexpensively and in a short time. The reason for the low cost is that the thin cast slabs have a thickness of 1.0-1.
That the cost for obtaining a 2 mm hot-rolled steel sheet is not high,
And that the hot-rolled steel sheet can be easily treated in the plating line.

According to the continuous plating method of claim 3
And to produce the required steel sheet at the desired cost.
Can be

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of the present invention,
It is a schematic diagram of a hot-dip galvanizing line. Fig. 1 (a)
(B) and (c) show the flow of a series of steel sheets in the line in order from the upstream side.

FIG. 2 is a schematic view showing a conventional general continuous galvanizing line.

[Description of Signs] 4 Pickling tank (Pickling means) 5 Cold rolling mill 6 Annealing furnace 7 Zinc bath pot (Plating means)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kozo Hirai 3-1-1 Higashi Kawasaki-cho, Chuo-ku, Kobe-shi, Hyogo Kawasaki Heavy Industries, Ltd. Kobe Plant (72) Inventor Hirotaku Nakamura Higashi-Kawasaki, Chuo-ku, Kobe-shi, Hyogo 3-1-1, Machi Kobe Plant, Kawasaki Heavy Industries, Ltd. F-term (reference) 4E002 BD02 BD10 CA08 CB10 4K027 AA02 AA22 AB42 AC02 AC18 AD01 AD28 AE11 4K053 PA02 PA12 QA01 RA05 RA14 TA02 TA09 TA16 TA20 XA34

Claims (4)

[Claims] 1. A continuous plating line for a steel sheet, comprising a pickling means and a cold rolling mill upstream of the plating means. 2. The continuous steel sheet plating line according to claim 1, wherein the cold rolling mill comprises one stand. 3. A hot-rolled steel sheet having a thickness of 1.2 mm or less,
3. A continuous plating method for a steel sheet, wherein pickling, cold rolling, and plating are continuously performed by passing through the continuous plating line according to claim 1 or 2. 4. A continuous plating method for a steel sheet, comprising using a hot-rolled thin cast slab obtained by continuous casting as said hot-rolled steel sheet.